Next set of split_common changes (#4974)

* Update split_common to use standard i2c drivers

* Eliminate RGB_DIRTY/BACKLIT_DIRTY

* Fix avr i2c_master error handling

* Fix i2c_slave addressing

* Remove unneeded timeout on i2c_stop()

* Fix RGB I2C transfers

* Remove incorrect comment

quantum/split_common/split_util.c

@@ -3,7 +3,6 @@
 #include "keyboard.h"
 #include "config.h"
 #include "timer.h"
-#include "split_flags.h"
 #include "transport.h"
 #include "quantum.h"
 
@@ -60,10 +59,6 @@ static void keyboard_master_setup(void) {
   #endif
 #endif
   transport_master_init();
-
-  // For master the Backlight info needs to be sent on startup
-  // Otherwise the salve won't start with the proper info until an update
-  BACKLIT_DIRTY = true;
 }
 
 static void keyboard_slave_setup(void)